Switching and timing unit for pneumatic relays



K. L. TATE 2,441,044

SWITCHING AND TIMING UN-IT FOR PNEUMATIC RELAYS Filed July 26, 1946 ympaz'azaal 022% fasi fase@ v Patented May 4, yg

man:

Kenneth Hl. Tate,

, G BNET FOR REHAYS N. Y.. assigner, by

:mesme ancients. to the United States oi `liinierilea as represend by the Unit States Altec Energy .u nl

ion

This invention relates to a pneumatic damping and switching unit. or like agement.

whereby the piping connections in apneumatic relay of the force-balance or other type can be simply interchanged so that the reset ilunction of the relay may be omitted, or the timing rate of said reset function may be changed to any one of several values.

The present invention has particular application to a so-called pneumatic reset relay oi the force-balance type, although it will be readily apparent that this invention is applicable to various types of pneumatic relays.

In the drawings, Fig. 1 is a diagrammatic showing of the parts oi. a pneumatic relay in side elevation, indicating one of several ways in which the damping unit of this invention can be connected therein; Fig. 1a and Fig. lb show other possible connections of the damping unit to the relay of Fig. 1; and Fig. 2 is a vertical section through the damping unit.

In the pneumatic relay herein illustrated, there is provided a so-called primary system compris ing a. bellows d into which a variable pressure. resulting from the deviation in a variable condition to be controlled, is introduced and also a bellows t into which there is introduced an` adjustable reference pressure that remains at a xed value ior any given adjustment. The bellows 5 and t preferably have their respective lower ends secured to a support S. The tops of the bellows are respectively attached to opposite ends of a rocker arm 'i which is adapted to rocl: about a iiexlble strip or spring pivot 8. The rocker arm is secured to a. primary lever arm il provided at its right-hand end (Fig. 1) with a baffle 6B. This bae cooperates with a nozzle ii to which compressed air is supplied from a source l2 through the restriction it.

The relay also includes a secondary system comprising bellows it and it, which are suitably mounted on the support S of the relay. The upper ends of the bellows it and it are. respectively. connected to the ends of a rocker arm il similar to rocker arm l, already described and adapted to rock about aexible strip or spring pivot it. The rocker arm li is secured to a secondary lever arm it which is connected to the primary lever arm t by a flexible connecting link 2G adjustable to the right or to the left to change the ratio of motion of the levers 9 and lil. The operation of the portion of thekk relay thus far described is similar to that already disclosed in the copending application of -Floyd B. Newelll Serial No. 668,304, iiled May 8, 1946, relating to is: adjusting arrangement for pneumatic relays of the force-balance type. structurally these parts of the pneumatic relay, herein diagrammatically disclosed, may be identical with those illustrated in the mentioned copending applicau tion.` except that herein the reset bellows it replaces the coil spring 22 in the device disclosed in the mentioned application.

The back pressure in the pipe 2t between the nozzle ii and the restriction it is introduced through pipe it and restriction 2t into bellows i5. The capillary restriction 2d is used in the pipe leading to the bellows it to stabilize the action of the relay. The back pressure in pipe @i and the chamber above the orifice it is used to control the process and is connected therewith through the output connection 23. A controlled pressure from an outside source is supplied through pipe 29, jumper 3i in the dampingunit' U and pipes 32 and it to bellows it. It will be understood that the relay is in equilibrium when the i'orce due to the pressure in-bellows t balances that due to the pressure in bellows t, both acting on 'rocker arm or beam i and at the same time force due to the pressure in bellows it balances that due to the pressure in bellows it, both 4 acting yon rocker arm or beam il. Under these H exist simultaneously. The first condition is that there is a difference between the forces due to the pressures in bellows 5 and t which supplies a torque` to the primary lever t. The second condition is that there is a diierence between the forces due to the pressures in the secondary bellows i5 and vit which supplies a torque to the secondary beam I9. The third condition is that the torques on the primary beam 9 and the secondary beam i9 are such that the forces at the connecting link 20 are equal and opposite.

A particular feature of the invention relates to the mentioned damping' unit U used for conveniently switching the pressure connections to different parts of the relay whereby the relay. under one set of connections, functions with a loading pressure supplied directly to the bellows i6 as in Fig. 1 or, under two other different sets of connections, as shown in Figs. 1a and 1b, with a pressure supplied through a restriction 25 in such away as to cause the relay to have either is annular in horizontal section to permit a holding screw 26 to pass axially therethrough. From the bottom ci the tank 21, which is otherwise sealed, there project iive prongs 28a, 28h, 28o, 28d and 28e. Prongs 28a and 28h are both hollow and are internally connected within the can 21 by the jumper or pipe. 3|. Prong 28e is also hollow and is internally connected with one end of the capillary resistance 25 which is coiled as shown in Fig. 2 and which communicates at its free end with the interior of the can 21. Prong 28d is hollow for connecting'the piping to the interior of the can, while prong 28e is solid. These prongs which have the appearance of the prongs of a socalled vacuum tube used in the radio art, plug into corresponding recesses or socket openings one of which openings ls not connected in the piping in the support S such blind socket opening serving to close ofi any open prong which is inserted therein. A suitable gasket (not shown) isused to prevent leakage between the tank and the support against which it is held tightly by means of the mentioned screw 2B. The tank can be separated from the base, and after rotation it can be plugged into the base in as many differ- .ent positions as there are pressure connections (in this example five), and several of these positions (in this example three consecutive ones) are used to make the proper connections in the piping to produce the desired result.

In this particular example, when the tank 21 containing the capillary 25, is set in position illustrated in the diagram of Fig. 1, the relay operates in proportional response without `reset and the pressure in bellows I6 is supplied from the outside pressure source, through pipe 29, jumper 3l and pipe l:i2 and 30. The other passages in the damping unit are closed capillary tube 25 being closed by the above mentioned blind socket.

When the damping unit is set in the position of Fig. 1a the relay operates in proportional response plus fast reset rate of eiect and the pressure in bellows i8 is supplied from the nozzle back pressure in the pipe 2|, through the pipes Il and 22, the tank space 35, the capillary restriction 25 and the pipes 26 and 30. Under this last specified condition the relay is automatically restored to a condition of equilibrium after a certain length of time which is determined by the amount of restriction in the capillary 25 and the volumeof the bellows i6 and attached piping.

When the damping unit is set in position shown in Fig. 1b, the relay operates in proportional response plus slow reset rate of effect and the pressure in bellows |8 is supplied from the nozzle back pressure in the pipe 2| through the pipes I4 and 22, restriction 25, tank space 35, pipes 32 and 30. In this case the volume 35 in the damping unit is added to that of the bellows IB and attached piping. When the tank S .is in this position, prong 28a is closed by the above mentioned blind socket.

l'll claim: f

1. In combination with a pneumatically-oper- I ated relay having pipes with terminals variably 1 :for certain hollow prongs, at least one of said prongs communicating directly with the interior of said tank, a second prong communicating with the interior of said tank through a resistance, said prongs being selectively insertible into said terminals. y

2. In combination with a pneumatically-operated relay having pipes with terminals variably connectible to certain parts oi the relay to conduct a pneumatic medium thereto, said parts being designed to have different operating characteristics depending on the presence or absence of'pneumatic damping therein as Well as on the time factor of said damping when present, and a damping unit comprising a tank sealed except for certain hollow prongs, at least one of said prongs communicating directly with the interior of said tank, a second prong communicating with the interior of said tank through a capillarytype resistance located within the tank, said prongs being selectively insertible into said terminals.

3. In combination with a pneumatically-operated relay having pipes with terminals variably connectible to certain parts of the relay to conduct a pneumatic medium thereto, said parts being designed to have diierent operating characteristics depending on the presence or absence of pneumatic damping therein as Well as on the time factor of said damping when present, and a damping unit comprising a tank sealed except for certain hollow prongs, at least one of said prongs communicating directly with the interior of said tank, a second prong communicating with the interior of said tank through a resistance, a third prong and a fourth prong communicating with each other through a pipe mounted within said tank, said prongs being selectively insertible into said terminals.

KENNETH L. TATE.

REFERENCES CITED The following references are oi record in the le of this patent: 

